next topic »

[on:]

I think it's a transistor...



It's from a 20 year old board. Can a datasheet be found for it and / or what is the modern-day equivilant to replace it with?

Also this:



I assume it's a 5v regulator. Will any 7805 regulator do as a replacement?

Thanks

[Reply #1 on:]

I assume it's a 5v regulator. Will any 7805 regulator do as a replacement?

Yes.

On your first pic maybe
http://datasheet.seekic.com/PdfFile/MC3/ON_Semiconductor_MC33064P-5G11586.pdf

Lefty

[Reply #2 on:]

Thanks Lefty

These two components are next to each other, just after a bridge rectifier and capacitors, the regulator first and the transistor / voltage sensor second, on a board that I suspect has suffered a voltage spike. It's a 20 year old heat recovery unit.

There's plenty of youtube videos on how to test faulty transistors, but how do I test it if it's a faulty voltage sensor?

[Reply #3 on:]

There's plenty of youtube videos on how to test faulty transistors, but how do I test it if it's a faulty voltage sensor?

I think you would have to wire it into a simple testing circuit as the datasheet might show examples of and test it's operation by manipulating the input voltage and seeing if the output signal changes at the proper input voltage points. It's a somewhat unusually component and not something you see in most general purpose power supplies. It's generally used to hold a micro-processor in reset mode until the main voltage has risen to a certain minimum value.

Lefty

[Reply #4 on:]

That's actually a very helpful comment, Lefty. There is a fault on this board that is keeping the heat recovery unit in permanant defrost mode, even though I've got the board set up on the bench with all its "peripherals" working correctly.

All the components on the board look OK, which is why I came to the conclusion that a voltage spike must have damaged something, so I am trying to identify the components with a view to testing / replacing them one by one.

I came to this forum because I was going to build an Arduino based replacement for the board, but I think that is beyond my skill set for the time being, so I'm carrying on trying to troubleshoot the old board.

[Reply #5 on:]

which is why I came to the conclusion that a voltage spike must have damaged something,

No components of that sort of age can suffer random failures nothing needs to have damaged it. It is rare that a faulty component can be identified just by looking at it. When you can, it is when it has suffered a catastrophic failure, either from external excess or damage that has occurred once it has failed and no longer is serving it's function.
Capacitors can also go but it is a bit more difficult to measure them in circuit.
Have you got any test equipment? A good scope is almost essential.